Three studies are going on: 1. The properties of a PurB mutant in E. coli which is a conditional antimutator for spontaneous mutations as well as some mutagens such as UV light. 2. The properties of an E. coli mutant mapping near 50 minutes in which stable RNA synthesis is temperature sensitive and some but not all m-RNA. 3. The description and analysis of some T7 genes that interact with E. coli genes and those of E. coli plasmids.